Sianesi et al., U.S. Pat. No. 3,350,373 discloses copolymers of 1,2,3,3,3-pentafluoropropylene and tetrafluoroethylene, a method for preparing them, and a process for melt forming shaped articles. Sianesi's polymers are crystalline polymers having 1,2,3,3,3-pentafluoropropylene comonomer concentrations of less than 20 mole percent.
Hrivnak et al., U.S. Pat. No. 6,248,823, discloses solvents for so-called amorphous fluoropolymers. Amorphous fluoropolymers include copolymers of TFE with perfluoromethylvinylether, perfluoroethylvinylether, perfluoropropylene (HFP), perfluorodimethyldioxole, perfluoro-2-(2-fluorosulfonylethoxy) propyl vinyl ether, and others. Solvents disclosed include fluorinated alkanes, fluorinated alkenes, fluorinated sulfides, hexafluorobenzene and others. Amorphous fluoropolymers are characterized by having no melting transition with a heat of fusion greater than 1 J/g as determined by differential scanning calorimetry (DSC). The HFP copolymers are ca. 48 mole percent HFP.
Tuminello et al., U.S. Pat. No. 6,767,626, discloses a method for protection of stone by preparing coated stone surfaces using substantially amorphous copolymers of hexafluoropropylene and tetrafluoroethylene.